JP2012201856A - Method for producing latex for dip molding, latex for dip molding, dip molding composition, and dip-molded product - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing latex for dip molding allowing for obtaining latex for dip molding having satisfactory characteristics without causing a production problem such as aggregates and adhesion of scales to a reactor can wall even when monomer concentration is increased.SOLUTION: The method for producing the latex for dip molding for copolymerizing a conjugated diene monomer, an ethylenically unsaturated nitrile monomer, an ethylenically unsaturated acid monomer and a monomer of a specific composition consisting of another ethylenically unsaturated monomer polymerizable with them includes: the steps of (1) initiating a first stage of polymerization using an initial polymerization monomer being a monomer occupying a specific proportion of the total monomers used and containing a specific proportion of the total amount of the ethylenically unsaturated acid monomer used for the polymerization, (2) adding a specific amount of an additional emulsifier to a polymerization system when a polymerization rate of the initial polymerization monomer is within a predetermined range, and (3) performing a second stage of the polymerization by sequentially adding the remaining monomer to the polymerization system after the addition of the emulsifier is completed.

Description

  The present invention relates to a method for producing a dip molding latex, a dip molding latex obtained thereby, a dip molding composition containing the dip molding latex, and a dip molded product, and more particularly, agglomeration during polymerization. A method for producing a latex for dip molding with a small change in viscosity at the time of pH increase capable of giving a dip molded product having sufficient strength by suppressing generation of matter and scale adhesion to the polymerization can wall, and a dip obtained by this production method The present invention relates to a molding latex, a dip molding composition containing the dip molding latex, and a dip molding obtained therefrom.

Conventionally, acrylonitrile-butadiene copolymer latex, which is a synthetic rubber latex obtained by emulsion polymerization, is used as a raw material for dip-molded products such as rubber gloves. Unlike rubber gloves obtained using natural rubber latex, rubber gloves obtained using acrylonitrile-butadiene copolymer latex are suitable for causing no allergic reactions or causing rashes or itchiness. Can be used for For this reason, the production amount of acrylonitrile-butadiene copolymer latex for dip molding has been greatly increased.
In producing such acrylonitrile-butadiene copolymer latex, the problem is how to improve the polymerization productivity, particularly from the viewpoint of cost. For this purpose, in the production by emulsion polymerization, it is important to increase the monomer concentration in the polymerization system (less water).
However, when the monomer concentration is increased, production problems such as a large amount of agglomerates and scales adhering to the reactor can wall and the properties of the resulting latex are not satisfactory for dip molding. There will be a quality problem.
For example, Patent Document 1 discloses an acrylonitrile-butadiene copolymer latex that gives a dip-molded product excellent in texture and tensile strength, and the amount of water is reduced in the polymerization method disclosed therein. It was found that scale adhered to the reactor can wall, and the resulting latex produced a large amount of microaggregates.

JP 2003-165814 A

Therefore, the object of the present invention is not to cause a production problem that even if the monomer concentration is increased, a large amount of agglomerates are produced or scales adhere to the reactor can wall, An object of the present invention is to provide a method for producing a dip molding latex capable of obtaining a dip molding latex having satisfactory characteristics for dip molding.
Another object of the present invention is to provide a dip molding latex obtained by this method for producing a dip molding latex and having satisfactory characteristics for dip molding.
Furthermore, another object of the present invention is to provide a dip molding composition comprising the dip molding latex.
Furthermore, another object of the present invention is to provide a dip-molded product having excellent characteristics using this dip-molding composition.

  As a result of diligent research, the present inventors have found that the above problems can be achieved by adopting a specific method for the addition of monomers and polymerization auxiliary materials in polymerization, and based on this finding, the present invention It came to complete.

Thus, according to the invention, 50-89.5 parts by weight of conjugated diene monomer, 10-40 parts by weight of ethylenically unsaturated nitrile monomer, 0.5-10 parts by weight of ethylenically unsaturated acid monomer and A method for producing a latex for dip molding in which 100 parts by weight of a monomer consisting of 0 to 19.5 parts by weight of another ethylenically unsaturated monomer copolymerizable with these is used, which is (1) used The first monomer is composed of 40 to 60% by weight of the total monomer and contains 40 to 60% by weight of the total amount of the ethylenically unsaturated acid monomer used for the polymerization. (2) When the polymerization conversion rate of the initial polymerization monomer is in the range of 40 to 70% by weight, 0.1 to 5 with respect to the total monomer weight used for the polymerization Add% emulsifier to the polymerization system, (3) after the addition of the emulsifier, Method for producing a dip molding latex and carrying out the second stage of polymerization successively added the extra monomer to the polymerization system is provided.
Moreover, according to this invention, the latex for dip shaping | molding obtained by the manufacturing method of the latex for dip shaping | molding of the said invention is provided.
Furthermore, according to the present invention, there is provided a dip molding composition comprising the dip molding latex of the present invention.
Furthermore, according to the present invention, there is provided a dip-molded product obtained by dip-molding the dip-molding composition of the present invention.

  According to the present invention, even if the monomer concentration is increased, the latex for dip molding can be produced without causing production problems such as formation of a large amount of aggregates and adhesion of scale to the reactor can wall. Using this latex for dip molding, a dip molding composition is prepared, and from this, a dip molded product having excellent characteristics can be obtained.

  The method for producing the latex for dip molding of the present invention comprises 50 to 89.5 parts by weight of a conjugated diene monomer, 10 to 40 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.5% of an ethylenically unsaturated acid monomer. A method for producing a latex for dip molding comprising copolymerizing 100 parts by weight of a monomer comprising 10 parts by weight and 0 to 19.5 parts by weight of other ethylenically unsaturated monomers copolymerizable therewith, (1) An initial polymerization monomer comprising 40 to 60% by weight of the total amount of monomers used and containing 40 to 60% by weight of the total amount of ethylenically unsaturated acid monomers used for polymerization (2) When the polymerization conversion rate of the initial polymerization monomer is in the range of 40 to 70% by weight, with respect to the total monomer weight used for the polymerization, Add 0.1-5% by weight of additional emulsifier to the polymerization system, (3) After serial emulsifier completion of the addition, and performing a second stage of the polymerization by sequential addition of monomer remaining in the polymerization system.

  The method for producing the latex for dip molding of the present invention comprises 50 to 89.5 parts by weight of a conjugated diene monomer, 10 to 40 parts by weight of an ethylenically unsaturated nitrile monomer, and 0.5% of an ethylenically unsaturated acid monomer. It consists of copolymerizing 100 parts by weight of monomers consisting of 0 to 19.5 parts by weight and 10 parts by weight of other ethylenically unsaturated monomers copolymerizable therewith.

  In the method for producing a dip-forming latex of the present invention, the polymerization method is not particularly limited, but an emulsion polymerization method in which a monomer is polymerized in the presence of water and an emulsifier is preferable.

The conjugated diene monomer used in the method for producing the latex for dip molding of the present invention is not particularly limited, and specific examples thereof include 1,3-butadiene, isoprene, 2,3-dimethyl-1,3-butadiene, Examples include 2-ethyl-1,3-butadiene, 1,3-pentadiene, and chloroprene.
These conjugated diene monomers may be used individually by 1 type, and may be used in combination of 2 or more type.
Among the above, 1,3-butadiene and isoprene are preferable as the conjugated diene monomer, and 1,3-butadiene is more preferable.

  The usage-amount of a conjugated diene monomer is 50-89.5 weight part with respect to 100 weight part of all the monomers used for superposition | polymerization. The amount of the conjugated diene monomer used is preferably 55 to 84 parts by weight, more preferably 65 to 81 parts by weight, and particularly preferably 70 to 80 parts by weight. If the amount is too small, the resulting dip-molded product is inferior in texture, and conversely if too large, the tensile strength is inferior.

The ethylenically unsaturated nitrile monomer used in the method for producing the latex for dip molding of the present invention is not particularly limited, and specific examples thereof include acrylonitrile, methacrylonitrile, fumaronitrile, α-chloroacrylonitrile, α-cyanoethylacrylonitrile. Etc.
These ethylenically unsaturated nitrile monomers may be used individually by 1 type, and may be used in combination of 2 or more type.
Of the above, the ethylenically unsaturated nitrile monomer is preferably acrylonitrile and methacrylonitrile, more preferably acrylonitrile.

  The amount of the ethylenically unsaturated nitrile monomer used is 10 to 40 parts by weight with respect to 100 parts by weight of all monomers used for polymerization. The amount of the ethylenically unsaturated nitrile monomer used is preferably 15 to 36 parts by weight, more preferably 18 to 27 parts by weight, and particularly preferably 18 to 24 parts by weight. If this amount is too small, the resulting dip-molded product is inferior in tensile strength, and conversely if too large, the texture is inferior.

The ethylenically unsaturated acid monomer used in the method for producing the latex for dip molding of the present invention is not particularly limited, and examples thereof include acidic groups such as carboxyl groups, sulfonic acid groups, and acid anhydride groups. And ethylenically unsaturated monomers.
Specific examples of the ethylenically unsaturated monomer containing a carboxyl group include ethylenically unsaturated monocarboxylic acid monomers such as acrylic acid and methacrylic acid; ethylenically unsaturated monomers such as itaconic acid, maleic acid, and fumaric acid. Examples of the polyvalent carboxylic acid monomer include ethylenically unsaturated polyvalent carboxylic acid partial ester monomers such as monobutyl fumarate, monobutyl maleate, and mono-2-hydroxypropyl maleate.
Specific examples of the ethylenically unsaturated monomer containing a sulfonic acid group include styrene sulfonic acid.
Specific examples of the ethylenically unsaturated monomer containing an acid anhydride group include ethylenically unsaturated polyvalent carboxylic acid anhydrides such as maleic anhydride and citraconic anhydride.
These ethylenically unsaturated acid monomers can also be used as alkali metal salts or ammonium salts.
These ethylenically unsaturated acid monomers may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these ethylenically unsaturated acid monomers, ethylenically unsaturated carboxylic acid monomers are preferred, ethylenically unsaturated monocarboxylic acid monomers are more preferred, and methacrylic acid is particularly preferred.

  The usage-amount of an ethylenically unsaturated acid monomer is 0.5-10 weight part with respect to 100 weight part of all the monomers used for superposition | polymerization. The amount of the ethylenically unsaturated acid monomer used is preferably 1 to 9 parts by weight, more preferably 1 to 8 parts by weight, and particularly preferably 2 to 6 parts by weight. If this amount is too small, the resulting dip-molded product is inferior in tensile strength, and conversely if it is too large, the texture and the durability of the adhesive state are inferior.

  Specific examples of the ethylenically unsaturated monomer copolymerizable with the conjugated diene monomer, the ethylenically unsaturated nitrile monomer and the ethylenically unsaturated acid monomer used in the method for producing the latex for dip molding of the present invention Examples are not particularly limited (hereinafter may be simply referred to as “other ethylenically unsaturated monomers”), and specific examples thereof include vinyl aromatic monomers, ethylenically unsaturated carboxylic acids. Examples thereof include ester monomers, ethylenically unsaturated amide monomers, alkyl vinyl ether monomers, and the like.

Specific examples of the vinyl aromatic monomer include styrene, alkyl styrene, vinyl naphthalene and the like.
The ethylenically unsaturated carboxylic acid ester monomer may be an ethylenically unsaturated monocarboxylic acid ester or an ethylenically unsaturated polyvalent carboxylic acid ester.
Specific examples of the ethylenically unsaturated monocarboxylic acid ester include acrylic acid ester monomers and methacrylic acid ester monomers (hereinafter, acrylic acid and methacrylic acid are collectively referred to as “(meth) acrylic acid”). And the like.
Typical examples of the (meth) acrylic acid ester monomer include (meth) acrylic acid alkyl ester and (meth) acrylic acid aryl ester.
In these (meth) acrylic acid alkyl esters and (meth) acrylic acid aryl esters, the hydrogen atom of the alkyl group or aryl group is substituted with a halogen atom, a hydroxyl group, an epoxy group, an amino group, a cyano group, an alkoxy group, or the like. It may be a thing.

  Specific examples of these (meth) acrylic acid alkyl esters include methyl (meth) acrylate, ethyl (meth) acrylate, butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate; (meth) acrylic acid. Trifluoroethyl, tetrafluoropropyl (meth) acrylate; hydroxyethyl, hydroxypropyl (meth) acrylate; glycidyl (meth) acrylate; dimethylaminoethyl (meth) acrylate; cyanomethyl (meth) acrylate, (meth) 2-cyanoethyl acrylate, 1-cyanopropyl (meth) acrylate, 2-ethyl-6-cyanohexyl (meth) acrylate, 3-cyanopropyl (meth) acrylate; methoxymethyl (meth) acrylate, (meth ) Ethoxyethyl acrylate, methomethacrylate Shi ethoxyethyl; and the like.

Specific examples of the ethylenically unsaturated polycarboxylic acid ester include an ethylenically unsaturated dicarboxylic acid diester and an ethylenically unsaturated tricarboxylic acid triester.
Specific examples of ethylenically unsaturated dicarboxylic acid diesters include maleic acid diesters such as diethyl maleate and dibutyl maleate; fumaric acid diesters such as diethyl fumarate and dibutyl fumarate; itaconic acid such as dimethyl itaconate and diethyl itaconate Diesters; and the like.

  Specific examples of the alkyl vinyl ether monomer include methyl vinyl ether, ethyl vinyl ether, n-propyl vinyl ether, isopropyl vinyl ether, n-butyl vinyl ether, isobutyl vinyl ether, cyclohexyl vinyl ether, fluoroethyl vinyl ether, 2,2,2-trifluoroethyl vinyl ether. 2,2,3,3,3-pentafluoropropyl vinyl ether and the like.

  Specific examples of the ethylenically unsaturated amide monomer include amide derivatives of (meth) acrylic acid, and typical examples thereof include (meth) acrylamide, N-methylol (meth) acrylamide, N, N. -Dimethylol (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-propoxymethyl (meth) acrylamide, etc. can be mentioned.

The other ethylenically unsaturated monomer may have a crosslinkable site in the molecule.
Specific examples of such monomers include polyvinyl aromatic monomers such as divinylbenzene; polyethylene glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, trimethylolpropane tri (meth) acrylate, pentaerythritol. And polyacrylate monomers such as (meth) acrylates.

One of these “other ethylenically unsaturated monomers” may be used alone, or two or more thereof may be used in combination.
The amount of other ethylenically unsaturated monomers used is 19.5 parts by weight or less with respect to 100 parts by weight of all monomers used for polymerization. The amount of other ethylenically unsaturated monomers used is preferably 14 parts by weight or less, more preferably 9 parts by weight or less. If this amount is too large, the balance between the texture of the resulting dip-molded product and the tensile strength is poor.

  In the method for producing a latex for dip molding according to the present invention, in the copolymerization of the above monomers, first, it is a monomer comprising 40 to 60% by weight of the total monomers used and is used for the polymerization. An initial polymerization monomer containing 40 to 60% by weight of the total amount of unsaturated acid monomers is charged into the polymerization reactor, and the first stage polymerization is preferably started in the presence of water and an emulsifier.

  In the method for producing a dip-forming latex of the present invention, the polymerization temperature is not particularly limited, but is usually 0 to 95 ° C, preferably 5 to 70 ° C.

  In the method for producing a dip molding latex of the present invention, a polymerization auxiliary material usually used in emulsion polymerization, such as a molecular weight modifier, a particle size modifier, a chelating agent, and an oxygen scavenger, is used as necessary. Can do.

  The usage-amount of the water used for superposition | polymerization is 80-500 weight part with respect to 100 weight part of all monomers, Preferably it is 100-300 weight part. Among these, in the polymerization of the initial polymerization monomer (first stage polymerization), the amount of water to be used is usually 60 to 400 parts by weight, preferably 70 to 200 parts by weight.

  The initial polymerization monomer should be 40 to 60% by weight of the total monomers used for the polymerization. The amount of the initial polymerization monomer is preferably 43 to 57% by weight, more preferably 45 to 55% by weight. If the amount is too large, the stability during polymerization is poor and aggregates are generated. Conversely, if the amount is too small, the desired tensile strength cannot be obtained when dip molding is performed.

  The initial polymerization monomer needs to contain 40 to 60% by weight of the total amount of the ethylenically unsaturated acid monomer used for the polymerization. The amount of the ethylenically unsaturated acid monomer is preferably 43 to 57% by weight, more preferably 45 to 55% by weight. If this amount is too large, after adjusting the pH of the latex for dip molding, the latex viscosity will rise and the dip moldability will deteriorate. Conversely, if it is too small, the desired tensile strength will be obtained when dip molding is performed. Absent.

The polymerization initiator is not particularly limited, and specific examples thereof include inorganic peroxides such as sodium persulfate, potassium persulfate, ammonium persulfate, potassium perphosphate, and hydrogen peroxide; diisopropylbenzene hydroperoxide, cumene hydroper Oxide, t-butyl hydroperoxide, 1,1,3,3-tetramethylbutyl hydroperoxide, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, di- Organic peroxides such as α-cumyl peroxide, acetyl peroxide, isobutyryl peroxide, benzoyl peroxide; azo compounds such as azobisisobutyronitrile, azobis-2,4-dimethylvaleronitrile, methyl azobisisobutyrate; Etc.
These polymerization initiators may be used individually by 1 type, and may be used in combination of 2 or more type.

Among the above polymerization initiators, the inorganic peroxide initiator is preferably used because it can stably produce a latex, and a dip-molded product having high mechanical strength and soft texture can be obtained.
Although the usage-amount of a polymerization initiator is not specifically limited, It is preferable that it is 0.01-1.0 weight part with respect to 100 weight part of all the monomers used for superposition | polymerization.

Moreover, a peroxide initiator can be used as a redox polymerization initiator in combination with a reducing agent. The reducing agent is not particularly limited, but is a compound containing a metal ion in a reduced state such as ferrous sulfate or cuprous naphthenate; a sulfonic acid compound such as sodium methanesulfonate; an amine compound such as dimethylaniline. And the like.
These reducing agents may be used individually by 1 type, and may be used in combination of 2 or more type.
Although the usage-amount of a reducing agent is not specifically limited, It is preferable that it is 0.03-10 weight part with respect to 1 weight part of peroxide initiators.

  The emulsifier used for polymerization is not particularly limited, and an anionic emulsifier, a nonionic emulsifier, a cationic emulsifier and an amphoteric emulsifier can be used. These emulsifiers may be so-called copolymerizable emulsifiers having a polymerizable group.

Specific examples of anionic emulsifiers include salts of fatty acids such as myristic acid, palmitic acid, oleic acid and linolenic acid; alkylbenzene sulfonates such as sodium dodecylbenzenesulfonate; higher alcohol sulfates; alkylsulfosuccinates; etc. Can be mentioned. Examples of the salt in these anionic emulsifiers include alkali metal salts and ammonium salts.
Specific examples of the nonionic emulsifier include polyoxyethylene alkyl ether, polyoxyethylene alkylphenol ether, polyoxyethylene alkyl ester, polyoxyethylene sorbitan alkyl ester and the like.

Specific examples of the cationic emulsifier include alkyltrimethylammonium chloride, dialkylammonium chloride, benzylammonium chloride and the like.
Specific examples of copolymerizable emulsifiers include sulfoesters of α, β-unsaturated carboxylic acids, sulfate esters of α, β-unsaturated carboxylic acids, sulfoalkylaryl ethers, and the like.

These emulsifiers may be used individually by 1 type, and may be used in combination of 2 or more type.
Among the above, anionic emulsifiers are particularly preferably used as the emulsifier.
The amount of emulsifier used during the initial monomer polymerization is 100 parts by weight of the initial polymerization monomer.
Usually, it is 0.2 to 8 parts by weight, preferably 0.3 to 6 parts by weight, and more preferably 0.5 to 4 parts by weight.

Next, when the polymerization conversion rate of the initial polymerization monomer is in the range of 40 to 70% by weight, 0.1 to 5% by weight of additional emulsifier is polymerized with respect to the total monomer weight used in the polymerization. Add to the system.
It is essential that this additional emulsifier is added when the polymerization conversion rate of the initial polymerization monomer is in the range of 40 to 70% by weight, preferably 45 to 65% by weight, more preferably 50 to 70% by weight. This is when it is in the range of 60% by weight. If the timing of addition is too early, the latex viscosity will increase and the dip moldability will be poor. Conversely, if the timing of addition is too late, the stability during polymerization will be poor and aggregates will be generated.

  The addition amount of this additional emulsifier is essential to be in the range of 0.1 to 5% by weight, preferably 0.2 to 3% by weight, more preferably based on the total monomer weight used in the polymerization. It is in the range of 0.5 to 2% by weight. If the amount added is too large, problems occur during dip molding due to foaming of the latex. Conversely, if the amount added is too small, the stability during polymerization is poor and aggregates are generated.

Here, the kind of the additional emulsifier to be added is not particularly limited, but it is preferable to use the one used for the polymerization of the initial polymerization monomer.
The method of adding the additional emulsifier is not particularly limited, but it is easy to operate as an aqueous solution.
Further, the additional emulsifier may be added all at once, or may be added over a certain period of time.

After the addition of the additional emulsifier is completed, the remaining monomer (which is obtained by removing the initial polymerization monomer from all the monomers used in the polymerization) is sequentially added to perform the second stage polymerization. Do.
Here, the sequential addition is a concept including both continuous addition in which a monomer is constantly added and intermittent addition in which a monomer is intermittently added.
When the remaining monomers are sequentially added, the composition of the monomers may be the same over the entire sequential addition time period or may be changed with time.

In the sequential addition of the remaining monomer, only the monomer may be added. However, it is preferable to add the monomer as an emulsion with an emulsifier from the viewpoint of maintaining the operation and polymerization stability.
At this time, the emulsion may be prepared usually using 10 to 200 parts by weight of water and 0.3 to 3 parts by weight of an emulsifier with respect to 100 parts by weight of the monomer.
The emulsifier used for preparing the emulsion is not particularly limited, but it is preferable to use the one used for the polymerization of the initial polymerization monomer.

After completion of the addition of the remaining monomer, the polymerization is continued until a predetermined polymerization conversion rate is obtained, and then the polymerization is terminated.
The polymerization conversion rate when stopping the polymerization reaction is preferably 90% by weight or more, more preferably 93% by weight or more.
The method for terminating the polymerization may be the addition of a polymerization terminator, and in the case of high temperature polymerization, the polymerization system temperature may be lowered.

The polymerization terminator is not particularly limited as long as it is usually used in emulsion polymerization.
Specific examples thereof include hydroxyamine compounds such as hydroxylamine, hydroxyamine sulfate, diethylhydroxyamine, hydroxyaminesulfonic acid and alkali metal salts thereof; sodium dimethyldithiocarbamate; hydroquinone derivatives; catechol derivatives; hydroxydimethylbenzenethiocarboxylic acid, And aromatic hydroxydithiocarboxylic acids such as hydroxydiethylbenzenedithiocarboxylic acid and hydroxydibutylbenzenedithiocarboxylic acid, and alkali metal salts thereof.
Although the usage-amount of a polymerization terminator is not specifically limited, Usually, it is 0.1-2 weight part with respect to 100 weight part of all the monomers.

  After stopping the polymerization reaction, the unreacted monomer is removed if desired, and the solid content concentration and pH are adjusted to obtain the latex for dip molding of the present invention.

According to the method for producing latex for dip molding of the present invention, scale does not adhere to the reactor can wall during polymerization, or even if it adheres, the amount is extremely small.
The dip molding latex of the present invention obtained by the dip molding latex production method of the present invention has a low agglomerate content, particularly an agglomerate content of 200 mesh or more, preferably dip molding. 0.01% by weight or less, and more preferably 0.005% by weight or less, based on the total solid content of the latex.

  In addition, the dip molding latex of the present invention obtained by the dip molding latex production method of the present invention has a small increase in viscosity when the pH is increased. For example, the latex has a solid content concentration of 45% and a viscosity at pH 8.3 of 50 mPa. / S or less, preferably 30 mPa / s or less, and more preferably 20 mPa / s or less.

  An anti-aging agent, preservative, antibacterial agent, dispersant and the like can be appropriately added to the latex for dip molding of the present invention as necessary.

  The number average particle diameter of the latex for dip molding of the present invention is preferably 60 to 300 nm, more preferably 80 to 150 nm. In addition, this particle diameter can be adjusted to a desired value by a method of adjusting the usage-amount of an emulsifier and a polymerization initiator.

  The dip molding composition of the present invention contains the above dip molding latex of the present invention.

The dip molding composition of the present invention preferably contains a vulcanizing agent and a vulcanization accelerator, and may further contain zinc oxide if desired.
As the vulcanizing agent, those usually used in dip molding can be used. Specific examples thereof include sulfur such as powdered sulfur, sulfur white, precipitated sulfur, colloidal sulfur, surface-treated sulfur, insoluble sulfur and the like; polyamines such as hexamethylenediamine, triethylenetetramine and tetraethylenepentamine; and the like. Of these, sulfur is preferable.
The amount of the vulcanizing agent used is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight, and particularly preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the latex solid content. .

As the vulcanization accelerator, those usually used in dip molding can be used.
Specific examples thereof include dithiocarbamic acids such as diethyldithiocarbamic acid, dibutyldithiocarbamic acid, di-2-ethylhexyldithiocarbamic acid, dicyclohexyldithiocarbamic acid, diphenyldithiocarbamic acid, dibenzyldithiocarbamic acid and zinc salts thereof; 2-mercaptobenzothiazole; 2-mercaptobenzothiazole zinc, 2-mercaptothiazoline, dibenzothiazyl disulfide, 2- (2,4-dinitrophenylthio) benzothiazole, 2- (N, N-diethylthiocarbaylthio) benzothiazole, 2- (2 , 6-Dimethyl-4-morpholinothio) benzothiazole, 2- (4'-morpholino-dithio) benzothiazole, 4-morpholinyl-2-benzothiazyl disulfide, 1, - bis (2-benzothiazyl mercaptomethyl) urea and the like. Of these, zinc dibutyldithiocarbamate, 2-mercaptobenzothiazole, and zinc 2-mercaptobenzothiazole are preferable.
One of these vulcanization accelerators may be used alone, or two or more thereof may be used in combination.
The use amount of the vulcanization accelerator is preferably 0.1 to 5 parts by weight, more preferably 0.3 to 3 parts by weight, and particularly preferably 0.5 to 2 parts by weight with respect to 100 parts by weight of the latex solid content. It is.

  The amount of zinc oxide used is preferably 5 parts by weight or less, more preferably 4 parts by weight or less, and particularly preferably 3 parts by weight or less with respect to 100 parts by weight of the latex solid content.

  The dip molding composition of the present invention may further contain a pH adjuster, a thickener, an anti-aging agent, a dispersant, a pigment, a filler, a softening agent, etc., which are usually blended as desired. Further, other latexes such as natural rubber latex and isoprene rubber latex can be used in combination as long as the object of the present invention is not impaired.

The solid content concentration of the dip molding composition of the present invention is preferably 20 to 40% by weight, more preferably 25 to 35% by weight.
The pH of the dip molding composition of the present invention is usually 8.5 to 12, preferably 9 to 11.

The dip-molded product of the present invention is formed by dip-molding the dip-molding composition of the present invention.
As the dip molding method, a normal method may be employed, and examples thereof include a direct dipping method, an anode adhesion dipping method, and a teag adhesion dipping method. Of these, the anode coagulation dipping method is preferred because a dip-molded product having a uniform thickness is easily obtained.

  In the case of the anode adhesion dipping method, for example, a dip-molding mold is immersed in a coagulant solution, the coagulant is attached to the surface of the mold, and then the dip-molding composition is immersed in the dip-molding composition, A dip-formed layer is formed on the substrate.

Examples of the coagulant include metal halides such as barium chloride, calcium chloride, magnesium chloride, zinc chloride, and aluminum chloride; nitrates such as barium nitrate, calcium nitrate, and zinc nitrate; acetic acid such as barium acetate, calcium acetate, and zinc acetate. Salts; sulfates such as calcium sulfate, magnesium sulfate, and aluminum sulfate; and the like. Of these, calcium chloride and calcium nitrate are preferable.
The coagulant is usually used as a solution of water, alcohol, or a mixture thereof. The coagulant concentration is usually 5 to 50% by weight, preferably 10 to 30% by weight.

  The obtained dip-formed layer is usually subjected to heat treatment and vulcanized. Before performing the heat treatment, it may be immersed in water, preferably 30 to 70 ° C. for about 1 to 60 minutes, to remove water-soluble impurities (for example, excess emulsifier and coagulant). This operation may be performed after heat-treating the dip-formed layer, but is preferably performed before the heat treatment from the viewpoint that water-soluble impurities can be more efficiently removed.

  The dip-molded layer thus obtained is subjected to a heat treatment for 10 to 120 minutes at a temperature of 100 to 150 ° C. and vulcanized. As a heating method, an external heating method using infrared rays or hot air or an internal heating method using high frequency can be employed. Of these, heating with hot air is preferred.

  A dip-molded product is obtained by detaching the vulcanized dip-molded layer from the dip-molding die. As the desorption method, it is possible to adopt a method of peeling from the mold by hand, or peeling by water pressure or compressed air pressure.

  After the desorption, heat treatment may be further performed at a temperature of 60 to 120 ° C. for 10 to 120 minutes.

  The dip-molded product may further have a surface treatment layer formed on the inner and / or outer surface thereof.

  As the dip-formed product of the present invention, one having a tensile strength of 25 MPa or more, preferably 30 MPa or more can be easily obtained.

  The dip-molded product of the present invention can have a thickness of about 0.03 to about 3 mm, and can be suitably used for a thin one having a thickness of 0.05 to 0.3 mm. Specifically, medical supplies such as nipples for baby bottles, syringes, conduits, and water pillows; toys and exercise equipment such as balloons, dolls, and balls; industrial articles such as pressure forming bags and gas storage bags; Examples include household, agricultural, fishery and industrial gloves; finger sack. It is particularly suitable for thin surgical gloves.

  The present invention will be described more specifically with reference to the following examples. Unless otherwise specified, “part” and “%” are based on weight.

  The amount of scale adhered to the can wall at the time of latex polymerization and various properties of the latex and the dip molded product were measured by the following methods.

[Amount of scale attached to the can wall]
After completion of the polymerization, the scale attached to the can wall and the stirring blade is visually observed.
[Viscosity of latex]
The latex is adjusted to a solid content concentration of 45% and pH is adjusted to 8.3, and measured using a B-type viscometer.

[Aggregate content of latex]
The exact solid content of the sample latex having a solid content of about 45% is measured, and about 100 g of the sample latex is precisely weighed, then filtered through a 200 mesh SUS wire mesh of known weight, and several aggregates on the wire mesh are measured. Wash with water to remove latex. After drying this at 105 ° C. for 60 minutes, its dry weight is measured.
The aggregate content is determined from the following equation (1).
Aggregate content (%) = {(A−B) / (C × D)} × 10,000 (1)
here,
A: Weight of wire mesh and dried aggregate after drying B: Weight of wire mesh C: Weight of sample latex D: Total solid content (%) of sample latex
It is.

[Tensile strength of dip molding]
(Preparation of test specimens for evaluating physical properties of dip-molded products)
In accordance with ASTM D412, a rubber glove-shaped dip-molded product was punched with a dumbbell (Die-C) to obtain a test piece.
(Tensile strength)
The test piece was pulled at a tensile speed of 500 mm / min using a Tensilon universal testing machine, and the tensile strength immediately before breaking was measured.

Example 1A
In a nitrogen-substituted pressure-resistant polymerization reactor, 13.5 parts of acrylonitrile as an initial polymerization monomer, 33.75 parts of 1,3-butadiene and 2.75 parts of methacrylic acid, 50 parts in total, t-dodecyl mercaptan as a molecular weight regulator (TDM) 0.5 parts, deionized water 95 parts, emulsifier sodium dodecylbenzenesulfonate (DBS) 1.0 part, polymerization initiator 0.2 parts potassium persulfate, and reducing agent sodium ethylenediaminetetraacetate ( EDTA) 0.1 part was charged. The temperature in the polymerization system was raised to 35 ° C. to initiate the polymerization reaction.
When the polymerization conversion reached 50%, 1.0 part of sodium dodecylbenzenesulfonate as an additional emulsifier was added all at once as a 10% aqueous solution.
After the addition of the additional emulsifier sodium dodecylbenzene sulfonate, 13.5 parts of acrylonitrile, 33.75 parts of 1,3-butadiene and 2.75 parts of methacrylic acid, a total of 50 parts (residual monomer) and t-dodecyl mercaptan An emulsion obtained by emulsifying 0.4 part with 15.0 parts of deionized water and 0.5 part of sodium dodecylbenzenesulfonate was continuously added to the polymerization system over 270 minutes. The polymerization conversion rate at the end of the continuous addition was 60%.
Thereafter, the polymerization was continued until the polymerization conversion rate of all monomers reached 97%, and then 0.1 part of diethylhydroxylamine was added to terminate the polymerization reaction.
After removing unreacted monomers from the obtained latex, the solid content concentration and pH were adjusted to obtain a latex 1A for dip molding having a solid content concentration of 45% and a pH of 8.3.
Table 1 shows the state of scale adhesion to the reactor can wall and stirring blade after the polymerization reaction, the amount of 200 mesh-on aggregates and the B-type viscosity of the resulting dip-forming latex 1A.

(Example 1B)
The dip-forming latex 1A was adjusted to a solid content of 40%, 250 parts (corresponding to 100 parts of solids), 1 part of sulfur, 1.5 parts of zinc oxide, 0.5 parts of zinc diethylcarbamate, water After mixing 8.66 parts of a vulcanizing agent dispersion prepared by mixing 0.03 parts of potassium oxide and 5.63 parts of water, an appropriate amount of 5% potassium hydroxide aqueous solution and deionized water were added to obtain a solid content. A dip molding composition 1B having a concentration of 30% and a pH of 9.8 was obtained.

(Example 1C)
On the other hand, the glove mold was immersed for 1 minute in a coagulant aqueous solution prepared by mixing 20 parts of calcium nitrate, 0.05 part of polyoxyethylene octylphenyl ether, which is a nonionic emulsifier, and 80 parts of water. And dried for 3 minutes to allow the coagulant to adhere to the glove mold. Next, the glove mold with the coagulant attached is dipped in the above dip molding composition 1B for 6 minutes and pulled up, and then the glove mold on which the dip molding layer is formed is dried at 25 ° C. for 3 minutes, and then 40 It was immersed in warm water at 0 ° C. for 3 minutes to elute water-soluble impurities. The glove mold was then dried at 80 ° C. for 20 minutes, and subsequently heat treated at 120 ° C. for 25 minutes to vulcanize the dip-formed layer. Finally, the vulcanized dip-formed layer was peeled off from the glove mold to obtain a glove-shaped dip-formed product 1C. Table 1 shows the evaluation results of the tensile strength of the dip-formed product 1C.

(Example 2A)
A latex 2A for dip molding was obtained in the same manner as in Example 1A, except that the composition of the initial polymerization monomer and the composition of the remaining monomers were changed as shown in Table 1.
Table 1 shows the state of scale adhesion to the reactor can wall and stirring blade after the polymerization reaction, and the amount of 200 mesh-on aggregates and B-type viscosity of the resulting dip-forming latex 2A.

(Example 2B)
Using the dip molding latex 2A, a dip molding composition 2B was obtained in the same manner as in Example 1B.

(Example 2C)
Using the dip molding composition 2B, a dip molded product 2C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-molded product 2C.

(Example 3A)
A latex 3A for dip molding was obtained in the same manner as in Example 1A except that the composition of the initial polymerization monomer and the composition of the remaining monomers were changed as shown in Table 1.
Table 1 shows the adhesion state of the scale to the reactor can wall and the stirring blade after the polymerization reaction, the amount of 200 mesh-on aggregates and the B-type viscosity of the resulting dip-forming latex 3A.

(Example 3B)
Using the dip molding latex 3A, a dip molding composition 3B was obtained in the same manner as in Example 1B.

(Example 3C)
Using the dip molding composition 3B, a dip molding 3C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-formed product 3C.

(Comparative Example 1A)
In a nitrogen-substituted pressure-resistant polymerization reactor, a total of 100 parts of all monomers used for polymerization of 27.0 parts of acrylonitrile, 67.5 parts of 1,3-butadiene, and 5.5 parts of methacrylic acid, 0.02 parts of t-dodecyl mercaptan. 5 parts, 150 parts of deionized water, 1.5 parts of sodium dodecylbenzenesulfonate, 0.2 part of potassium persulfate and 0.1 part of sodium ethylenediaminetetraacetate were charged. The temperature in the polymerization system was raised to 35 ° C. to initiate the polymerization reaction.
When the polymerization conversion reached 50%, 1.0 part of sodium dodecylbenzenesulfonate as an additional emulsifier was added all at once as a 10% aqueous solution.
Thereafter, the polymerization was continued until the polymerization conversion rate of all monomers reached 97%, and then 0.1 part of diethylhydroxylamine was added to terminate the polymerization reaction.
After the unreacted monomer was distilled off from the obtained latex, the solid content concentration and pH were adjusted to obtain a dip-forming latex C1A having a solid content concentration of 45% and a pH of 8.3.
Table 1 shows the state of scale adhesion to the reactor can wall and the stirring blade after the polymerization reaction, the amount of 200 mesh-on aggregates and the B-type viscosity of the resulting dip-forming latex C1A.

(Comparative Example 1B)
Using the dip molding latex C1A, a dip molding composition C1B was obtained in the same manner as in Example 1B.

(Comparative Example 1C)
Using the dip molding composition C1B, a dip molded product C1C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-molded product C1C.

(Comparative Example 2A)
A latex C2A for dip molding having a solid content concentration of 45% and a pH of 8.3 was obtained in the same manner as in Comparative Example 1 except that the amount of deionized water during polymerization was reduced from 150 parts to 110 parts.
Table 1 shows the state of scale adhesion to the reactor can wall and the stirring blade after the polymerization reaction, the amount of 200 mesh-on aggregates and the B-type viscosity of the resulting dip-forming latex C2A.

(Comparative Example 2B)
Using the dip molding latex C2A, a dip molding composition C2B was obtained in the same manner as in Example 1B.

(Comparative Example 2C)
Using the dip molding composition C2B, a dip molding C2C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-molded product C2C.

(Comparative Example 3A)
A nitrogen-substituted pressure-resistant polymerization reactor was charged with 95 parts of deionized water, 0.5 part of sodium dodecylbenzenesulfonate and 0.1 part of sodium ethylenediaminetetraacetate, and the temperature in the polymerization system was raised to 35 ° C.
Next, 27.0 parts of acrylonitrile, 67.5 parts of 1,3-butadiene and 5.5 parts of methacrylic acid in total 100 parts in total and 0.5 part of t-dodecyl mercaptan were added to deionized water. Continuous addition of emulsion prepared using 15.0 parts and 0.5 parts sodium dodecylbenzenesulfonate (addition rate: 10 parts / hour) was started.
15 minutes after the start of continuous emulsion addition, 0.2 part of potassium persulfate was added to initiate polymerization.
When the continuous addition of the emulsion was completed, 1 part of sodium dodecylbenzenesulfonate as an additional emulsifier was added as a 10% aqueous solution.
Thereafter, the polymerization was continued until the polymerization conversion rate of all monomers reached 97%, and then 0.1 part of diethylhydroxylamine was added to terminate the polymerization reaction.
After the unreacted monomer was distilled off from the obtained latex, the solid content concentration and pH were adjusted to obtain a latex C3A for dip molding having a solid content concentration of 45% and a pH of 8.3.
Table 1 shows the state of scale adhesion to the reactor can wall and stirring blade after the polymerization reaction, and the amount of 200 mesh-on aggregates and B-type viscosity of the resulting dip-forming latex C3A.

(Comparative Example 3B)
Using the dip molding latex C3A, a dip molding composition C3B was obtained in the same manner as in Example 1B.

(Comparative Example 3C)
Using the dip molding composition C3B, a dip molding C3C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-molded product C3C.

(Comparative Example 4A)
The amount of methacrylic acid during the polymerization of the initial polymerization monomer was changed from 2.75 parts to 5.5 parts, and the amount of methacrylic acid in the remaining monomer was changed to zero. Thus, a latex C4A for dip molding having a solid content concentration of 45% and a pH of 8.3 was obtained.
Table 1 shows the state of scale adhesion to the reactor can wall and the stirring blade after the polymerization reaction, the amount of 200 mesh-on aggregates and the B-type viscosity of the resulting dip-forming latex C4A.

(Comparative Example 4B)
Using the dip molding latex C4A, a dip molding composition C4B was obtained in the same manner as in Example 1B.

(Comparative Example 4C)
Using the dip molding composition C4B, a dip molding C4C was obtained in the same manner as in Example 1C. Table 1 shows the evaluation results of the tensile strength of the dip-formed product C4C.

From the results shown in the table, the following can be understood.
According to the method for producing a dip molding latex of the present invention, there is no generation of scale or aggregate in the latex, the viscosity of the latex after pH adjustment does not increase, and the obtained dip molding latex The tensile strength of the dip-molded product obtained from the above is also good (Examples 1 to 3).
On the other hand, when all monomers are added at once and polymerized, when the solid content concentration is 40%, there is no generation of scales or aggregates in the latex, the viscosity of the latex and the dip-formed product. The tensile strength of is also equivalent to those of the present invention (Comparative Example 1). However, when the solid content concentration is increased in order to improve the polymerization productivity of the latex, a large amount of scale during polymerization and generation of aggregates in the latex are observed.
When all the monomers are added continuously, there is no generation of scale or agglomerates in the latex during polymerization, and the viscosity of the resulting latex is equivalent to that of the present invention, but the tensile strength of the resulting dip-molded product is Compared with that of the present invention, it is greatly reduced (Comparative Example 3).
Similar to the polymerization method of the present invention, even when a method of starting polymerization using an initial polymerization monomer and then adding an emulsifier and then polymerizing the remaining monomer is employed, When the composition is out of the range specified in the present invention, there is no generation of scale or aggregate in the latex during polymerization, and the tensile strength of the resulting dip-molded product is equivalent to that of the present invention, but the latex obtained The viscosity increases significantly (Comparative Example 3).

Claims (4)

  50-89.5 parts by weight of conjugated diene monomer, 10-40 parts by weight of ethylenically unsaturated nitrile monomer, 0.5-10 parts by weight of ethylenically unsaturated acid monomer, and others copolymerizable therewith It is a manufacturing method of the latex for dip-molding which copolymerizes 100 weight part of monomers which consist of 0 to 19.5 weight part of ethylenically unsaturated monomer, Comprising: (1) 40 ~ of all the monomers used The first stage polymerization is started using an initial polymerization monomer containing 60 to 60% by weight of a monomer consisting of 60% by weight and containing 40 to 60% by weight of the total amount of the ethylenically unsaturated acid monomer used for the polymerization, (2) When the polymerization conversion rate of the initial polymerization monomer is in the range of 40 to 70% by weight, 0.1 to 5% by weight of additional emulsifier is polymerized with respect to the total monomer weight used in the polymerization. (3) After the addition of the emulsifier is completed, the remaining monomer is added to the polymerization system. Method for producing a dip molding latex and carrying out the polymerization of the second stage was added.   A latex for dip molding obtained by the method for producing a latex for dip molding according to claim 1.   A dip-forming composition comprising the dip-forming latex according to claim 2.   A dip-molded product obtained by dip-molding the dip-molding composition according to claim 3.